Quasi-Van der Waals Epitaxial Growth of γ'-GaSe Nanometer-Thick Films on GaAs(111)B Substrates.

GaSe is an important member of the post-transition-metal chalcogenide family and is an emerging two-dimensional (2D) semiconductor material. Because it is a van der Waals material, it can be fabricated into atomic-scale ultrathin films, making it suitable for the preparation of compact, heterostructure devices. In addition, GaSe possesses unusual optical and electronic properties, such as a shift from an indirect-bandgap single-layer film to a direct-bandgap bulk material, rare intrinsic p-type conduction, and nonlinear optical behaviors. These properties make GaSe an appealing candidate for the fabrication of field-effect transistors, photodetectors, and photovoltaics. However, the wafer-scale production of pure GaSe single-crystal thin films remains challenging. This study develops an approach for the direct growth of nanometer-thick GaSe films on GaAs substrates by using molecular beam epitaxy. It yields smooth thin GaSe films with a rare γ'-polymorph. We analyze the formation mechanism of γ'-GaSe using density-functional theory and speculate that it is stabilized by Ga vacancies since the formation enthalpy of γ'-GaSe tends to become lower than that of other polymorphs when the Ga vacancy concentration increases. Finally, we investigate the growth conditions of GaSe, providing valuable insights for exploring 2D/three-dimensional (3D) quasi-van der Waals epitaxial growth.

A Solvent Exchange Induced Robust Wet Adhesive Hydrogels to Treat Solid Tumor Through Synchronous Ethanol Ablation and Chemotherapy.

The treatment of tumors in developing countries, especially those with poor medical conditions, remains a significant challenge. Herein, a novel solvent-exchange strategy to prepare adhesive hydrogels for the concurrent treatment of tumors through synchronous ethanol ablation and local chemotherapy is reported. First, a poly (gallic acid-lipoic acid) (PGL) ethanol gel is prepared that can undergo solvent exchange with water to form a hydrogel in situ. PGL ethanol gel deposited on the wet tissue can form a hydrogel in situ to effectively repel interfacial water and establish a tight contact between the hydrogel and tissue. Additionally, the functional groups between the hydrogels and tissues can form covalent and non-covalent bonds, resulting in robust adhesion. Furthermore, this PGL ethanol gel demonstrates exceptional capacity to effectively load antitumor drugs, allowing for controlled and sustained release of the drugs locally and sustainably both in vitro and in vivo. In addition, the PGL ethanol gel can combine ethanol ablation and local chemotherapy to enhance the antitumor efficacy in vitro and in vivo. The PGL ethanol gel-derived hydrogel shows robust wet bioadhesion, drug loading, sustained release, good biocompatibility and biodegradability, easy preparation and usage, and cost-effectiveness, which make it a promising bioadhesive for diverse biomedical applications.

A portable microfluidic device for thermally controlled granular sample manipulation.

Effective granular sample manipulation with a portable and visualizable microfluidic device is significant for lots of applications, such as point-of-care testing and cargo delivery. Herein, we report a portable microfluidic device for controlled particle focusing, migration and double-emulsion droplet release via thermal fields. The device mainly contains a microfluidic chip, a microcontroller with a DC voltage control unit, a built-in microscope with a video transmission unit and a smartphone. Five microheaters located at the bottom of the microfluidic chip are used to unevenly heat fluids and then induce thermal buoyancy flow and a thermocapillary effect, and the experiments can be conveniently visualized through a smartphone, which provides convenient sample detection in outdoor environments. To demonstrate the feasibility and multifunctionality of this device, the focusing manipulation of multiple particles is first analyzed by using silica particles and yeast cells as experimental samples. We can directly observe the particle focusing states on the screen of a smartphone, and the particle focusing efficiency can be flexibly tuned by changing the control voltage of the microheater. Then the study focus is transferred to single-particle migration. By changing the voltage combinations applied on four strip microheaters, the single particle can migrate at predetermined trajectory and speed, showing attractiveness for those applications needing sample transportation. Finally, we manipulate the special three-phase flow system of double-emulsion drops in thermal fields. Under the combined effect of the thermocapillary effect and increased instability, the shell of double-emulsion droplets gradually thins and finally breaks, resulting in the release of samples in inner cores. The core release speed can also be flexibly adjusted by changing the control voltage of the microheater. These three experiments successfully demonstrate the effectiveness and multifunctionality of this thermally actuated microfluidic device on granular manipulation. Therefore, this portable microfluidic device will be promising for lots of applications, such as analytical detection, microrobot actuation and cargo release.